Thermostatic switch



March 5, 1935. c. A. LANDIN THERMOSTATIC SWITCH Filed Jan. 50, 1931 2 Sheets-Sheet l :by 4,7 MVV-Tg gwuentoz Car/ A 0770727 March 5, 1935. C, A, LANDW 1,993,275

THERMOSTATIC SWITCH Filed Jan'. 3o, 1931 2 sheets-sheet 2 a* MM Patented Mar. 5, 1935 UNITED STATES PATENT @FFICE 1,993,275 'THERMOSTATIC SWITCH Carl A. Landin, West Hartford, ionn., assigner to The Hart Manufacturing Company, Harta ford, Conn., a corporation of Connecticut Appliation January so, 193i, seriai No. 512,266

l Claims.

ing means, such as a pointer, operated by the thermostatic element for indicating the temperature of the apparatus which is to be controlled. As an instance of a use to which the device of the present invention may be applied, reference may be had to the controlling and indicating of the temperatures of an electrically heated oven or the like. It is to be understood, however, that the present invention is not limited to this speciiic use, as it has a wide application and may be used in connection with various industrial or household installations,

An aim of the invention is to provide a device of this sort which is characterized by its signal eiliciency in operation, in that .it will quickly and accurately respond to temperature changes Within the chamber, the temperature of which is to be controlled, and will operate to keep that chamber at a substantially uniform selected temperature within the desired range.

Another object of the invention is to provide an improved device which is very reliable in performing its functions for long periods of time without liability of the parts becoming deranged or deteriorating. The improved arrangement is such that there is but very little burden on the thermostatic element in the operation of the switch and that element is relatively free to expand and contract at all times.

A still further aim of the invention is to provide an improved thermostatically controlled circuit maker and breaker which may be very easily and quickly adjusted and read.

Another aim of the invention is to provide a device of this sort which is characterized by its extreme simplicity in construction and economy in manufacture, and by its durability, the device comprising but a relatively few in number of simple parts which may be readily assembled in a compact arrangement.V

Other objects will be in part obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction, combination of elements nd arrangement of parts which will be exempliiied in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

In the accompanying drawings, wherein is shown one of the embodiments which the present invention may take:

Figure 1 is a front View of my improved thermostatic switch, the cover or cap of the casingl being omitted;

Fig. 2 is a top plan view with the cover in place;

Fig. 3 is a side elevational view with parts' in section;

Fig. is a detail view similar to Fig. l but showing the switch as having been opened by the thermostat;

Fig. 5 is a sectional view taken on line 5 5 oi' Fig. l; and Y Fig. 6 is a sectional view taken on line 6 6 of Fig. 3.

Referring to the drawings in detail, 10 designates a support of any suitable kind and which may be in the form oi a base plate of a casing. The casing may have a cover or cap 11 of. suitable configuration. Extending rearwardlyk from the base plate and fixed thereto is a perforated pipe 12 Within which is housed a thermostatic element 13 which is here shown, for illustrative purposes, as being in the form of a bimetallic coil or helix, one end of which is suitably connected to an adjustable pin or anchor member la. The forward end of the coil 13 is connected to a shaft l5 journalled adjacent its rear end in a partition 16. The forward end of the shaft is journalled in, and extends through, a bushing 1'; tted in the forward end of the pipe l2 and having a circular flange or head 18 abutting against the front face of the base plate. Adjacent ends of the pin 14 and the shaft 15 have cylindrical heads or enlargements 14.' and 15' transversely slotted. The thermostatic member has its end portions respectively surrounding these enlargements and it has its extreme ends slidably engaging in the slots thereof, an aru rangement which does not form any particular part of the present invention. For the purpose of closely Calibrating the thermostatic member, the pin 14 is mounted for rotatable adjustment and, to this end, it may have a bearing in a plug 19 closing the rear end .ofthe pipe 12. The pin may be fixed in any position of adjustment by a set screw 20, as shown most clearly in Fig. 6.

Located above the shaft and pivoted on the base plate is the switch means which is here shown for illustrative purposes as being in the form of a mercury switch comprising a transparent tube having a pair of spaced wells in its bottom Wall into which extend the respective terminals 26 and 27. The *circuit closing member comprises a fluid body, such as a mass of mercury 24. Ihis mercury switch is of an old and wellknown construction. It is carried by a holder 28 formed of -sheet metal. The holder has two pairs of spring fingers 29 and 30 between which the glass tube is held. Secured to the bottom of the clip or holder is a flat wearfplate 31. The mercury switch is pivoted on a pin 32 which extends forwardly and horizontally from the base plate. The pivot 32 is so located that that end of the mercury switch, which has the terminals, tends to swing downwardly to and from a horizontal position; that is to say, the pivot 32 is spaced to one side of the center of mass of the switch so that the latter, under the force of gravity, will tend to swing about the pivot. The numeral 33 designates a collar about the pin 32 and between the base plate and the holder.

Secured to the forwardly projecting, end of the shaft 15 is an operating member 34 for moving the mercury switch to oi position under the influence of the thermostatic element 13. In the present illustrative disclosure, the forward end of the member 34 is in the form of a cam, the cam having a concentric circular portion 37 of one diameter and a concentric circular portion 38 of larger diameter, there being between these portions a shoulder or rise 39. The member 34 has al through opening which closely receives the forward end of the shaft 15, and the member is adapted to be secured in any desired position of angular adjustment upon the shaft by any suitable means, as by a set screw 40. The rear end of the member 34 abuts against the forward end of the bushing 17.

Journalled on the circular iiange 18 of the fixed bushing 17 is a setting member or lever 45, the

j free end of which has a pointer 46 which cooperthe setting lever.

ates with an arcuate scale 47. This scale bears suitable graduations with accompanying indicia for indicating temperatures. The free end of the setting lever also carries a handle or finger piece 48 by means of which the lever may be adjusted.

` Pivoted to the setting lever 45 and interposed between the operating cam vand the mercury switch is an operative lconnection comprising a lever 50 which preferably is of arcuate shape. This lever 50 is pivoted, as at 51, to the setting lever, and it has an external edge 52 curved generally concentrically to the axisvof rotation of This edge, adjacent the free end of the lever, departs somewhat from a concentric curve; that is, it straightens out slightly in order that the switch will lbe thrown to the same extent when it rests on the outer end of this curve as it does when it rests on the edge more closely to the pivot of the connecting lever.

The wear plate 31 rests upon this edge 52 at a point which is preferably substantially above the shaft 15. Carried by the connecting lever 50 is an abutment in the form of a roller 53 engaging the portions 37` and 38 of the operating cam. In order to frictionally hold the setting lever in its adjusted position, any suitable means may be provided, but by way of example, the spring finger 54 is disclosed: This spring finger is secured to the ,base plate by a screw, and its upper end is adapted to bear against the forward face of the setting lever. 'I'he terminals of the switch may be' connected by iiexible wires 56 to flxed terminals 57. n

For the purpose of indicating, at al1 times, the temperature prevailing within the chamber to be controlled, there is provided a pointer 60 secured to the operating cam (or the shaft 15) in an adjustable manner and having its upper end 61 cooperating with the scale 47. By way of illustration, this pointer Vis shown as being secured to the forward end of the cam by screws 62 extending through arcuate slots 63 in the pointer.

The operation of the device is briey as follows: The temperature, 4to which the oven or other mechanism or chamber is to be heated, having been determined, the setting lever 45 will be turned until the pointer 46 thereof is brought opposite that mark on the scale' 47 which indicates the desired temperature. Thus, the distance between the roller 53 and the rise 39 of the cam is adjusted. The switch rests upon the connecting lever 50, and the roller of that lever engages the periphery of the cam portion 37 so that the switch is held in horizontal position and in which the mercury closes contact between the terminals 26 and 27. The heating element within the oven is now on and, as the temperature of the oven rises, the thermostatic element will turn the cam 'counterclockwise When the cam is lthus turned, the parts will retain the position just described until the rise 39 is brought against the roller 53, whereupon the cam turns the connecting lever about the pivot 51 and the switch will be tilted counterclockwise about the pivot 32. Of course, the arrangement may be reversed. When the switch is thus tilted, the mercury will iiow to the left hand and now lower end of the tube, thus breaking the connection between the terminals 26 and 27 and shutting off the current within the Voven. In the event the heat within the oven should continue to rise, the switch mechanism for the thermostat would not be affected 'because the roller 53 will merely ride on the concentric surface 38 of the cam. After the heat is turned off, the temperature of the oven will drop, with the result that the thermostatic element will turn the cam clockwise until the shoulder 39 leaves the roller, whereupon the parts will be brought back to the position shown in Fig. 1, the current being again turned onto the oven. In Fig. 4, the parts are shown as being in off position, the adjustment of the setting lever being different from that shown in Fig. 1. The collar 33 constitutes a stop against which the lever 45 engages when the latter is moved to its extreme-right hand position. In actual practice and during normal operation, the extent of rotary movement of the cam, after the oven has reached the desired temperature, will be relatively small, and the rise 39 will be closely adjacent to or will engage the roller during the relatively slight changes of temperature within the oven. l

From the foregoing description, taken in connection with the accompanying drawings, it will be observed that the switch, including the mercury tube and its holder, at all times rests upon and directly engages the connecting lever, and the connecting lever is always held in correct operative relation to the controlling cam, which is turned under the influence of the thermostatic element. Thus, these parts automatically assume and retain their correct positions relative to one another, and there is no lost motion between the connecting lever and the switch holder which would be likely to introduce errors in the operation of the device. The apparatus is generally uniform in its operation in all positions of adjustment of the setting lever. The setting lever may be adjusted without affecting the thermostatic element, a feature of importance because, with this arrangement, the device may be initial- Iy calibrated with great accuracy, and that calibration is not later affected by the setting lever. Also, this feature permits of a very simple, effective arrangement. When the setting lever is adjusted, there are no strains or stresses set up in the thermostat which would aiect its operation or useful life.

It is further important to note that, during the normal functioning of the device, the thermostat is relatively free from strains, there being practically no strain on the thermostatic element, while the roller of the connecting lever is engaging either of the cam surfaces of the operating cam. The only time that there is a strain on the thermostatic element is when the shoulder` 39 of the cam engages the roller of the connecting lever. This strain is relatively slight and, for all practical purposes, can be ignored.

Further features of importanceare the extreme simplicity of the arrangement, and the ease and facility with which it may be adjusted to operate to any desired temperature within the selected range.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specic features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim as-my invention:

1. In a thermostatically operated switch, a. fixed support, a mercury switch pivoted thereto, a scale, thermostatic means, an operating member connected thereto and adapted to be turned thereby, a setting member adjustable independently of said operating member and ther'mostatic means and having a pointer cooperating with said scale, and an operative connection between said operating member and switch and including an element adjustable in unison with said setting member, said element being adapted to be moved relative to said setting member by said operating member.

2. In a thermostatically operated switch, in combination, a pivoted mercury switch, a thermostatic means, an operating member connected to and actuated by said thermostatic means, a setting member adjustable independently of said operating member, and a connecting member between said operating member and switch and adapted to tilt said switch on its pivot.

3. In a thermostatically operated switch, .a switch having an element with a fixed pivot, thermostatic means, an operating member connected thereto and rotated thereby, a setting member adjustable relative to said element and operating member, and a member pivoted to said setting member and interposed between said operating member4 and switch.

4. In^`a thermostatically operated switch, a switch comprising a pivoted mercury tube, thermostatic means, an operating member associated with and adapted to be turned by said thermostatic means, a setting member adjustable independently of said operating member and mercury tube, and a connecting member carried by, so as to be adjusted with, saidr setting member,

said connecting member being movable relative to said setting member by said operating member, and said connecting member having engagement with said switch whereby the latter is tilted when the connecting member is moved by said operating member.

5. In a thermostatically operated switch, a pivoted mercury switch, thermostatic means, an:

operating member associated with and rotated by said thermostatic means, and a connecting member mounted for adjustment with respect to, without changing the position of said operating member and the pivot of said switch, said connecting member being supported and moved by said operating member, and said switch being urged against and resting upon said connecting member.

6. In a thermostatically operated switch, a thermostatic element, a cam connected to and adapted to be rotated by said element; a connecting member cooperating with said cam and adapted to be moved thereby, said member being adjustable about the axis of said cam and independently of said cam;I and a switch having an velement resting upon said connecting member.

7. In a thermostatically operated switch, a thermostatic element, a cam connected thereto and adapted to be rotated thereby and having a rise in its periphery, a setting lever adjustable about the axis o said cam, a connecting lever movably carried by, and adjustable with, said setting lever and having an abutment cooperating with said cam, and a pivoted mercury switch resting on said connecting lever.

8. In a thermostatically operated switch, a thermostatic element, a cam adapted to be rotated thereby and having a rise in its perihery, a setting member adjustable about the same axis as said cam, a connecting lever pivoted on said setting lever and having a roller engaging the periphery of said cam and also having a curved surface, and a pivoted mercury switch normally urged towards, and adapted to rest upon, said surface.

9. In a thermostatically operated switch, a L

thermostatic element, a cam rotated thereby and having on its periphery concentric portionsof diierent diameters and a rise therebetween, a setting lever adjustable about the same axis as Said cam, a connecting lever pivotally carried by said setting lever and having an abutment resting against the periphery of said cam, said lever having a curved edge, and a pivoted mercury switch having one end resting on, and supported by, said edge.

lil. In a thermostatically` operated switch, a xed support, a mercury switch pivoted thereto, a scale, thermostatic means, an operating member connected thereto and adapted to be turned thereby, a setting member adjustable independently of said operating member and switch and having a pointer cooperating with said scale, and a connecting member between said operating member and switch.

ll. In a thermostatically operated switch, a fixed support, a switch pivoted on said support and comprising a mercury tube, a scale, thermostatic means, an operating member connected kthereto and rotated thereby, an adjustable setlil 12. In a thermostatcally operated switch, a support, a switch comprising a mercury tube pivoted to said support, a scale, thermostatic means, an operating member associated with and adapted to be turned by'sad thermostatic means and located beneath said switch, a setting lever adjustable independently of said operating member, a connecting member carried by so as to be adjusted with said setting lever, said connecting member being movable relative to said set` ting lever by said operating member, and said connecting member having' engagement with said switch whereby the latter is tilted when the connecting member is moved by said operating member, and a pointer adjustably secured to said operating member.

13. In a thermostatically operated switch, a fixed scale, a thermostatic element, a shaft rotated thereby, a cam secured to said shaft and having a rise in its periphery, 'an adjustable setting lever having a pointer cooperating with said scale, a connecting lever movably carried by and adjustable with said setting lever and having an abutment cooperating with the periphery of said cam, a pivoted mercury switch adapted to rest upon said connecting lever, and a pointer adjustably carried by said shaft and cooperating with said scale. i

14. In a thermostatically operated switch, a support, a fixed scale, a thermostatic element, a shaft rotated therebyp a cam secured to said shaft and having on its periphery concentric portions of different diameters and a rise therebetween, a setting lever adjustable about the same axis as said cam and having a pointer cooperating with said scale, a connecting lever plvotally carried by said setting lever and having an abutmentcooperating with the periphery of said cam, said lever having a curved edge, and a mercury switch pivoted to said support and having one end resting on, and supported by, said edge.

15. yIn a thermostatically operated switch, a vertical base plate, a shaft journalled therein, a bearing surface about said shaft forwardly of said base plate, a thermostatic coil connected at one end to said shaft and adjustably anchored at its other end, a cam adjustably secured to the forward end of said shaft and having on its periphery concentric portions of different diameters and a rise therebetween, a scale carried by said base plate, a setting lever journalled on said surface and engaging the front face of said base plate, frictional means engaging said lever. said setting lever having a pointer cooperating with ting lever and having a roller engaging the periphery of said cam and also having an external edge curved generally concentrically to said shaft, a mercury switch pivoted to said base plate and having one end normally urged downwardly under the force of gravity, said end of said switch engaging said edge substantially above said shaft, and an adjustable pointerl adapted to rotate with said cam and cooperating with said scale.

CARL A. LANDIN.

said scale, a connecting lever pivoted to said sety 

